1. Field of the Invention
This invention relates to an improvement on an illuminating system of an ophthalmological instrument.
2. Prior Art of the Invention
A conventional illuminating system of an ophthalmological instrument such as a microscope for use in operation comprises an observation-use coaxial illuminating system for projecting an observation-use illuminating light from a direction parallel to the optical axis (so-called coaxial direction in a sense that it illuminates through a lens-barrel of an objective lens) of an objective lens of an observating optical system toward an eye to be tested, and an observation-use oblique illuminating system for projecting an observation-use illuminating light from an oblique direction different from the coaxial illumination toward the eye through a slit to effect an oblique direction eye illumination (hereinafter referred to as the "oblique illumination"). In the illuminating system of this conventional ophthalmological instrument, a light source of the observation-use oblique illuminating system and a light source of the observation-use coaxial illuminating system are separately provided, and a switch for switching the light source of the observation-use illuminating system to the light source of the observation-use coaxial illuminating system, or vice versa is located in a position far away from an operator.
However, in this kind of illuminating system of an ophthalmological instrument, because the light source of the observation-use oblique illuminating system and the light source of the observation-use coaxial illuminating system must be separately prepared, a housing for containing the illuminating system of the ophthalmological instrument becomes too large. Therefore, when this is employed in an operation-use microscope, the large housing often becomes an obstacle during operation. Moreover, because the switch for the respective light sources is located in a position far away from the operator, it is difficult for the operator to rapidly switch the oblique illumination over to the coaxial illumination, or vice versa. In order to effect a switch-over operation rapidly, an assistance of a nurse, etc. is necessary and thus inconvenient.
As another prior art, there is known an illuminating system of an ophthalmological instrument which comprises the observation-use coaxial illuminating system and a photographic-use coaxial illuminating system for projecting a stroboscopic light toward an eye to be tested from the same direction to its illuminating direction in order to illuminate the eye.
In this conventional device, there is provided a quick return mirror for switching the optical path of the observation-use coaxial illuminating light to the optical path of the photographic-use stroboscopic light, or vice versa so as to guide the observation-use illuminating light to an objective lens of an observing optical system of a microscope during observation and to guide a stroboscopic light to the objective lens during photographing.
By the way, there is a case in which the eye is preferably illuminated from a direction different from the coaxial direction, i.e., from an oblique direction. In a case like this, if an observation-use oblique illuminating system for effecting an oblique illumination and a photographic-use oblique illuminating system are made as one pair, and if these are separately provided from one pair consisting of an observation-use coaxial illuminating system for effecting a coaxial illumination and a photographic-use illuminating system, an observation-use light source, a stroboscopic light source, a quick mirror for switching optical paths, etc. must be provided separately. This eventually makes the illuminating apparatus of an ophthalmological instrument too large and complicated. In addition to that, the costs become high and thus not preferable.